const arr = new Array(Math.floor(Math.random() * 20)).fill(null).map((_, index) => index + 1)
console.log('i++');
for (let i = 0; i < arr.length; i++) {
    console.log(arr[i]);
}
console.log('++i');
for (let i = 0; i < arr.length; ++i) {
    console.log(arr[i]);
}
let i = 0
if(i++) console.log('i++', i);
else if(++i) console.log('++i', i);
